The present development relates to a modular electrical device and, more particularly, to a modular electrical device that is highly resistant to ingress of water, oil, debris, dirt and other contaminants encountered in manufacturing and other environments without use of a separate enclosure. As described herein, one application for a device formed in accordance with the present development is as a modular distributed input/output (I/O) assembly that forms a part of or is connected to an industrial automation control system. Those of ordinary skill in the art will recognize that the device has other applications, and it is not intended that the device be limited to use for any particular application.
In connection with industrial automation control systems and other electrical systems, it has been deemed desirable to provide electrical devices for transmission/input/output of data signals and/or power voltages that are distributed throughout a manufacturing, distribution or other facility and located directly on or adjacent machines performing manufacturing, distribution, inspection and/or other processes. It has also been found that, in certain cases, these electrical devices should be modular to allow for customization, re-configuration and repair/replacement as needed during installation or later. This modularity improves usability but can lead to ingress of water, oil, dirt, debris, and/or other contaminants into the device, with highly undesirable consequences. Furthermore, modular components can undesirably separate owing to vibration, impact, cable stresses or other external forces.
Certain modular electrical devices are housed within an enclosure that provides secure mounting and also protects the device from environmental contamination. Use of an enclosure is often not practicable due to space constraints, ease of installation/re-configuration/repair and/or other concerns.
Contamination-resistant modular electrical devices are known. One example is a distributed input/output (I/O) assembly available commercially from Rockwell Automation under the trademark 1798 FLEX Armor™. I/O circuitry is packaged in I/O modules, and the I/O modules of an assembly plug into a common baseplate. The baseplates is available in sizes of 2, 4, 6, and 8 I/O module slots. An I/O adapter module and a field termination module plug into two slots of the baseplate. The baseplate holds the modules in place and provides the backplane for the assembly. No enclosure is required because each module is packaged in a sealed housing rated for IP65/67 and NEMA 4 X (indoor/outdoor) and 6 P. While the FLEX Armor™ I/O system has enjoyed widespread commercial success, certain modifications have been deemed desirable, at least for particular applications. For example, with the FLEX Armor™ system, the baseplates are available in units of 2, 4, 6 and 8 I/O modules. Also, to maintain the environmental ratings, all slots on the baseplate must be filled with either a live I/O module or a filler module.
Other modular electrical devices that are resistant to environmental contamination are known and available commercially from other sources. Some of these devices rely on conventional O-ring seals or other types of seals that provide only a single sealing dynamic at each sealing location, i.e., only radial/lateral sealing or only axial/compressive sealing. In certain cases, these seals are susceptible to leakage, especially when the modular components are subjected to vibration or other external forces such as lateral and/or axial separation forces. Other known devices utilize conventional O-rings seals or other seals that are positioned in a manner where they can be damaged or dislodged during handling, installation or during repair/replacement operations. Another drawback associated with some of these conventional modular electrical devices is that the seal is connected to or forms a part of the permanent components of the system, instead of the replaceable components. As such, use of a replacement component does not automatically result in use of a new seal. Known modular electrical devices have also been found to be sub-optimal insofar as operative mating of the components is concerned. Some require use of separate fasteners such as screws or the like which can be inconvenient and can lead to component damage if the fasteners are over-torqued. Other systems rely on a simple friction fit between components, and this can lead to unintended separation of the components such as when the components are mounted in an inverted position and/or in response to cable strain. Known systems have also not provided base components that are conveniently and securely mechanically with each other to ensure proper definition of the module mounting locations and to minimize undesired movement between base components. Examples of known modular electrical devices can be found in the following documents: U.S. Pat. No. 6,475,036; U.S. patent application Publication No. 2002/0182942; U.S. Pat. No. 4,707,043; German Utility Model No. DE29703367U1; and, German Utility Model No. DE29607525U1.
In light of the foregoing, it has been deemed desirable to provide a new and improved modular base for an electrical device, and/or an electrical device including the modular base and removable modules with improved operative mating of components so as to facilitate use and improve ingress protection.